A mobile communication terminal of frequency division duplex (FDD) type uses a duplexer that simultaneously performs transmission and reception via a single antenna. The duplexer is equipped with a reception filter and a transmission filter. These filters are formed by acoustic wave resonators, for example. The acoustic wave resonators may be surface acoustic wave resonators, boundary acoustic wave resonators, or piezoelectric thin-film resonators. The piezoelectric thin-film resonators are also called film bulk acoustic resonators.
Japanese Patent Application Publication Nos. 2003-332884 and 2006-74202 describe a configuration directed to improving the power durability in which an acoustic wave resonator close to an input terminal is divided into parts connected in series with each other.
A poor linearity of the duplexer may degrade the receiver sensitivity of the communication equipment.